The present invention relates generally to enclosures for interconnecting at least one optical fiber of a feeder cable with two or more optical fibers of a distribution cable. More particularly, the invention relates to a closure comprising a plurality of coupler modules for splitting an optical signal carried by an optical fiber of a feeder cable into different optical signals carried on two or more optical fibers of a distribution cable at a local convergence point in an optical network.
Telecommunications service providers are currently developing networks consisting entirely of fiber optic components to meet the demand for high bandwidth communications service to businesses and homes. These xe2x80x9call-opticalxe2x80x9d telecommunications networks require a line of service enclosures, referred to herein as xe2x80x9cclosures,xe2x80x9d along the network that are located at access points in the field. Each such location is referred to herein as a xe2x80x9clocal convergence point.xe2x80x9d A closure is utilized at a local convergence point to interconnect optical fibers of a feeder cable from a service provider with optical fibers of one or more distribution cables. In some instances, optical fibers of the feeder cable are connected to optical fibers of drop cables that are routed directly to the business or home of a subscriber of the communications service. In other instances, optical fibers of the feeder cable are connected to optical fibers of a cable that is routed from the closure to yet another local convergence point along the optical network to serve as a further feeder cable for additional drop cables. The further feeder cable is sometimes referred to in the art as a xe2x80x9cbranchxe2x80x9d cable. The optical network may be configured in many different ways, but typically, is configured with a plurality of feeder cables from the service provider having optical fibers that are interconnected with optical fibers of distribution cables at various local convergence points. The distribution cables serve as drop cables routed directly to communications equipment belonging to subscribers, or as branch cables routed to other local convergence points. As used herein, the term xe2x80x9cdistribution cablexe2x80x9d includes both drop cables and branch cables, as those terms are presently understood by one skilled in the art. Furthermore, the term xe2x80x9coptical fiberxe2x80x9d or xe2x80x9coptical fibersxe2x80x9d as used herein includes coated and uncoated (i.e., bare) single fibers, jacketed fibers (e.g., tight-buffered and loose buffered), multiple fibers, multiple fiber ribbons, and fiber optic cables containing one or more optical fibers.
While fiber optic networks have traditionally served as the back bone or trunk line of telecommunication networks to transmit signals over relatively long distances, all-optical networks are gradually being extended closer to the end points of the network. In this regard, fiber optic networks are being developed that deliver fiber-to-the-home, fiber-to-the-business, fiber-to-the-desk, and the like. In each of these applications, the closure must be capable of interconnecting optical fibers of the feeder cables with optical fibers of the distribution cable to establish the desired optical connections. In existing optical networks, the optical fibers of the feeder cable are typically interconnected with the optical fibers of the distribution cable within a splice closure that is buried underground, mounted in an above-ground pedestal, mounted on a telephone pole, or suspended from an aerial telephone cable strand. In the case of an underground (also referred to as below grade) splice closure, the closure typically includes a frame defining a longitudinal axis that is enclosed by a cylindrical or dome-shaped cover. In the case of a splice closure mounted on a telephone pole or suspended from an aerial telephone cable strand (also referred to as an xe2x80x9caerial closurexe2x80x9d), the closure typically includes a base defining a longitudinal axis and a cover movably attached to the base. The cover is intended to protect the optical fiber connections from adverse environmental conditions, while at the same time optimize the number of connections that can be made within the closure. In a splice closure, however, the optical fibers of the feeder cable are spliced in a one-to-one relationship with the optical fibers of the distribution cable. Thus, the number of optical connections that can be made within the splice closure, commonly referred to in the art as the xe2x80x9cfiber capacityxe2x80x9d of the closure, is limited by the number of one-to-one splices that can be accomplished within the volume constraints of the closure. As the all-optical network proliferates, it is anticipated that the number of optical connections required to be made within the closure will soon exceed the fiber capacity of conventional splice closures.
It is further anticipated that demand will require the number of optical fibers of the feeder cable to increase dramatically as the all-optical network proliferates. Since many feeder cables are already installed in fiber optic cable ducts that are buried underground, and because there is oftentimes a physical or functional limit to the number of optical fibers that can be contained together within a feeder cable, there will soon be too few optical fibers from service providers to meet the increased demand for high bandwidth communications service to businesses and homes. It will therefore be necessary, for example, for service providers to install additional feeder cables within existing fiber optic cable ducts or to invest in the construction of additional fiber optic cable ducts to carry the additional feeder cables. In either case, substantial capital expense will have to be incurred by the service provider, and ultimately, passed on to the subscriber in the form of higher cost communications service.
As the all-optical network proliferates, there will certainly be an increased need for a field technician to reconfigure the optical connections within the splice closure. Although spliced optical connections can be reconfigured, it is time consuming for the field technician to identify the appropriate optical fibers of the feeder cable and the distribution cable. Furthermore, it generally requires the expertise of a highly trained field technician to reconfigure a conventional splice closure at an access point in the field. As a result, it is costly for a service provider to frequently dispatch a skilled field technician to reconfigure the optical connections within a conventional splice closure. Once again, the additional expense incurred by the service provider to reconfigure the splice closure will ultimately be passed on to the subscriber in the form of higher cost communications service. Accordingly, there is a need for a closure that resolves the aforementioned difficulties associated with the proliferation of an all-optical telecommunications network. The present invention solves these, as well as other, problems by providing a closure for interconnecting at least one optical fiber of a feeder cable with two or more optical fibers of a distribution cable at a local convergence point in an optical network. The closure permits the optical connections to be made in a space efficient, organized and timely manner that does not require a highly skilled field technician to reconfigure the optical connections within the closure.